I recently tried to load a vCard file where several addresses had an identical UID. KAddressBook seemed to load the file just fine, but several entries were missing. It turned out that the missing entries had a duplicated UID with another field.

I know that this is an error in the file, but it would be very helpful if KAddressBook noticed this error, and printed an appropriate message.

Background: I regularly export my data from KAddressBook via a small script: https://github.com/tbleher/vcard-tools/blob/master/akonadi-to-vcard
I recently tried to re-import the generated vCard file on another computer, and noticed the error there. Apparently, duplicate UIDs are stored in the Akonadi database itself (as far as I could see, when an entry is copied). Now I don't know if this is a bug (because I don't know the internal akonadi format), and certainly the way the script accesses the data is not officially supported, but I thought the issue would still be worth mentioning.

I often export my data

Reproducible: Always

Steps to Reproduce:
1. Load vCard file which contain several entries, where some entries contain duplicate UID

Actual Results:  
Some addresses are missing

Expected Results:  
All addresses are there, or a warning is generated